A nonvolatile storage device including a re-writable nonvolatile memory is increasing in its demand mainly for use in semiconductor memory card. A nonvolatile storage system using the semiconductor memory card is also increasing in its demand mainly for use in digital still camera and personal computer.
A practical semiconductor memory card usually includes a flash memory as a nonvolatile memory and a controller LSI as its control circuit, inside. Recently, in the trend of larger capacity of semiconductor memory card, the nonvolatile memory chip is also increased in capacity by multiple-value configuration. Owing to the progress in mounting technology, the number of chips of nonvolatile memory mounted on the semiconductor memory card is increasing. For example, the memory space of semiconductor memory card is exceeding 1 GB.
As address management method for semiconductor memory card, a distributed management method has been used in the prior art. The “distributed management method” is a method of storing, in a management area of a page being a writing unit, a logical address or a status flag of its page, and generating an address management table based on the logical address or the status flag of page to store the address management table in the RAM in the controller LSI at the time of initialization. The logical address or the status flag of page is collectively called “distributed management information”.
However, in the semiconductor memory card having a memory space of large capacity, a much time is taken for reading out distributed management information of the whole memory space at the time of initialization. As a result, it may exceed the upper limit of standard initialization time in the semiconductor memory card, or cause other violation of standard. In particular, in a semiconductor memory card not specified by standard, if not violating the standard, the user suffers a huge demerit due to waiting time until accessible. Still more, the capacity of RAM for temporarily storing the address management table or the like is enormous, and there is a problem of cost.
To avoid such problems, a “centralized management method” is proposed, and its technology is disclosed in patent document 1. In the nonvolatile storage device of patent document 1, an address space of nonvolatile memory mounted on the semiconductor memory card is divided into a plurality of address ranges, a plurality of address management tables corresponding to the address ranges are stored in the nonvolatile memory, and the corresponding address management table is read out into the RAM depending on the write or erase command in specified logical address from a host.
Patent document 2 discloses a method of employing both distributed management method and centralized management method of storing collectively address management tables in the nonvolatile memory. The method and apparatus disclosed in patent document 2 are not intended to write back the address management table to the nonvolatile memory on every write command from the host or access device, but are intended to write back the address management table to the nonvolatile memory at a specified timing free of access such as power off, and judge the efficacy of address management table at the time of initialization, and to use the address management table if effective, or generate an address management table based on distributed management information if not effective.
Patent document 1: JP-A-2001-142774
Patent document 2: JP-A-11-73379